The invention relates to a circuit breaker having a housing. The housing includes a housing shell and a closure shell attached thereto to form a hollow chamber therebetween. The closure shell and the housing shell each have an inside wall surface extending parallel to a shell plane. Also provided are n-1, where n is an integer greater than 1, intermediate housing shells inserted between the housing shell and the closure shell and having first and second wall surfaces corresponding to the housing shell wall surface and the closure shell wall surface, respectively. The first wall surface faces the closure shell wall surface and the second wall surface faces the housing shell wall surface to form n hollow pole chambers. A switching mechanism for tripping the circuit breaker is provided. The switching mechanism includes a switch lever located within each pole chamber comprising at least one of a trip lever and a latching lever. Each switch lever is attached to a respective wall surface and is axially seated to pivot in a plane of movement extending approximately parallel to the shell plane. Each switch lever is coupled together for common triggering of all poles.
A circuit breaker of this type shown in European Patent Disclosure EP-B-0,208,613. The circuit breaker housing disclosed therein includes two outer shells, namely a housing shell and a closure shell that can be attached thereto. The switching mechanism is disposed between the two shells. Trip-free release of the circuit breaker is possible when overcurrent occurs, for example, by means of a bimetallic strip connected to the switching mechanism.
If needed, the single-pole circuit breaker with a pole chamber that is formed between the housing shell and the closure shell can be expanded to a multipole circuit breaker that has a corresponding number of pole chambers. For this purpose, one or a plurality of structurally identical intermediate housing shells are inserted between the housing shell and the closure shell. The partial region of the intermediate housing shell facing the housing shell corresponds structurally to the closure shell. The intermediate housing shell is therefore attached to the housing shell in the same manner as the closure shell. The partial region of the intermediate housing shell facing the closure shell corresponds structurally to the housing shell. In this way the single-pole circuit breaker can be expanded to a circuit breaker having an arbitrary number of poles.
The same switching mechanism is located in each pole chamber. To permit a common triggering of all poles of the circuit breaker, the identical switch levers of all of the pole chambers that cause the opening and closing of the electrical contacts are coupled with one another. The coupling parts are cylindrical pins integral to the switch levers and having a longitudinal axis that extends perpendicularly to the shell plane. A pin is seated on the shells in each pole chamber in the manner of a shaft. To transmit the torque of the triggering switch lever onto the identical switch levers of the other pole chambers, directly adjacent pins engage each other with their pin ends facing one another.
Coupling the switch levers by way of shafts of this type is, however, very disadvantageous. The pins of n pole chambers cooperate as an n-piece shaft. During the rotation of this shaft, friction losses occur between the engaging pins. Further friction losses occur in the bearing bores on the side of the shell for seating the individual pins. Overall, great frictional torques result that continuously reduce the torque of the triggering switch lever to be transmitted in the horizontal assembly direction of the shaft. As the specific number of poles increases, the remaining torque to be transmitted becomes so small that the switch levers disposed at a distance from the directly triggering switch levers no longer trip.
Moreover, the mechanical stability of each pin is reduced by its own torsion moments. The torsion moments additionally reduce the torque to be transmitted. Furthermore, it is expensive to construct the shells of the circuit breaker to permit a problem-free rotational movement of the pins. In this case the diameter of the bearing bore, that is, the amount of bearing play, must be taken into account. Because of production-related influences, however, the desired seating is not always assured, thus creating a danger of a skewed position of the pin with respect to its bearing bore. This effect intensifies to correspond to the number of poles of the circuit breaker. In extreme cases skewed pins can even damage the shells. Warming inside the pole chambers results in deformation of the bearing bores, further impairing the seating of the pins.